Flu Vaccine may Protect Against Heart Attacks
Reported September 28, 2009
(Ivanhoe Newswire) — Flu can trigger heart attacks and cause cardiovascular death, but the influenza vaccine may offer protection for cardiac patients.
Researchers say greater efforts are needed to encourage people with heart disease and diabetes (which increases the risk of heart attacks) to have the flu shot, especially with the looming double-whammy of the H1N1 influenza (swine flu) pandemic and seasonal flu outbreaks.
The cardiac complications of influenza infection, such as myocarditis, are well known, but the role of influenza as a trigger of heart attacks is less clear. It has been suggested that influenza might cause acute and severe inflammation, which in some patients may destabilize atherosclerotic plaques and cause clots in coronary arteries leading to heart attacks.
Charlotte Warren-Gash and Andrew C. Hayward from the UCL Centre for Infectious Disease Epidemiology, London, and Liam Smeeth from the London School of Hygiene and Tropical Medicine, conducted a systematic review of the evidence to examine the association between influenza and heart attacks or cardiovascular death, including the possible cardio-protective effects of the influenza vaccine. They analyzed 42 papers describing 39 studies between 1932 and 2008.
All the population-level studies showed a rise in deaths due to heart disease or heart attack during times when the influenza virus was circulating. The proportion of excess influenza deaths that were due to heart disease averaged 35 percent.
Four out of eight studies also showed a protective effect against heart attacks or cardiovascular events in those vaccinated against influenza. In addition, two small randomized trials suggested that influenza vaccination reduces the risks of cardiovascular death and some cardiac events.
The authors concluded: “We believe influenza vaccination should be encouraged wherever indicated, especially in those people with existing cardiovascular disease. . . . Further evidence is needed on the effectiveness of influenza vaccines to reduce the risk of cardiac events in people without established vascular disease.”
SOURCE: The Lancet Infectious Diseases, October 2009